Compensation control method and system for combustion cycle in natural gas engine cylinder

Abstract

The invention discloses a natural gas engine in-cylinder combustion cycle compensation control method and system, and the method comprises the steps: carrying out the calibration of a rack and a whole vehicle, and recording the preset signals of misfire and knocking; detecting an engine knock signal and an engine misfire signal, comparing the engine knock signal and the engine misfire signal with a misfire and knock preset signal, judging whether knock or misfire exists at present or not, and correcting the EGR rate and the ignition advance angle according to the knock signal and the misfire signal if knock or / and misfire are / is judged; and measuring an air humidity value through an atmospheric environment sensor, comparing the air humidity value with an air humidity preset value, judging whether the current humidity is abnormal or not, if the humidity is abnormal, correcting the EGR rate and the ignition advance angle, and then returning to the previous step. Through monitoring knock, misfire and humidity signals, interactive processing is carried out, a compensation correction strategy is executed, the combustion cycle fluctuation ratio in an engine cylinder is effectively reduced, and the operation stability of an engine is improved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic control of natural gas engines, and in particular to a method and system for controlling a combustion cycle compensation in a cylinder of a natural gas engine. Background Art

[0002] At present, the National VI natural gas engines on the market basically adopt the equivalent combustion + EGR (exhaust gas recirculation) + TWC (three-way catalytic converter) route. The engine development is carried out on the bench based on the standard environment to conduct relevant engine performance tests and electronic control calibration to ensure that the performance of the engine product reaches the expected level of development. After the development under the standard environment of the bench is completed, it will enter the three-high calibration link and finally output the final electronic control data. However, after the engine is put on the market, the operating conditions change rapidly. The standard environment of the bench and the three-high calibration road conditions cannot cover the road conditions of normal vehicles in actual use. When the engine is running in certain special environments, such as mountainous areas after high temperature and rain in Sichuan in summer, the actual water vapor content entering the cylinder will change due to excessive air humidity, resulting in poor combustion in the cylinder, increased fluctuation rate of the cycle in the cylinder, and even fire, causing serious faults such as panting of the whole vehicle and burning of the catalyst.

[0003] The information disclosed in the above background technology section is only intended to increase the understanding of the overall background of the present invention, and should not be regarded as admitting or suggesting in any form that the information constitutes the prior art already known to ordinary technicians in this field. Summary of the invention

[0004] In view of the above-mentioned existing defects, the purpose of the present invention is to provide a natural gas engine in-cylinder combustion cycle compensation control method and system, which monitors knock, misfire and humidity signals for interactive processing and executes compensation correction strategies, thereby effectively reducing the combustion cycle fluctuation rate in the engine cylinder and improving the engine operation stability.

[0005] The technical solution of the present invention is as follows:

[0006] A natural gas engine cylinder combustion cycle compensation control method, comprising:

[0007] S1: Perform bench knock calibration, bench misfire calibration, and vehicle misfire calibration, and record the preset signals of misfire and knock respectively;

[0008] S2: Detect the engine knock signal through the knock sensor, detect the engine misfire signal through the crankshaft speed sensor, compare with the preset signals of misfire and knock, and judge whether it is knock or misfire at present. If it is knock and / or misfire, correct the EGR rate and ignition advance angle according to the knock signal and misfire signal; if it is neither knock nor misfire, enter S3;

[0009] S3: Measure the air humidity value through the atmospheric environment sensor, compare it with the preset air humidity value, and determine whether the current humidity is abnormal. If the humidity is abnormal, correct the EGR rate and ignition advance angle, and then return to S2; if the humidity is normal, the normal operation signal of the whole vehicle is prompted.

[0010] Furthermore, in S2, the EGR rate and the ignition advance angle are corrected according to the knock signal and the misfire signal, specifically including:

[0011] S201: If it is judged that there is knock but not misfire, the ignition advance angle of the single cylinder is reduced or EGR is increased until the knock is normal, and then it is judged whether there is misfire. If there is misfire, the process goes to S202;

[0012] S202: If misfire does not cause knock, increase the ignition advance angle or reduce EGR for each cylinder until misfire becomes normal, and then determine whether there is knock. If there is knock, proceed to S201;

[0013] S203: If both detonation and misfire occur, the ignition advance angle of the single cylinder is increased or decreased, and then it is determined whether there is detonation or misfire. If there is detonation or misfire, an abnormal operation signal of the whole vehicle is prompted, and the engine torque is limited to the limit threshold.

[0014] Furthermore, in S4, the EGR rate and the ignition advance angle are corrected, specifically including:

[0015] If the humidity is higher than the preset value t1, the horizontal bar increases the ignition advance angle or reduces EGR;

[0016] If the humidity is lower than the preset value t2, the single bar reduces the ignition advance angle or increases EGR.

[0017] The present invention also provides a natural gas engine cylinder combustion cycle compensation control system, which adopts the above-mentioned method, including: an engine body, EGR, a supercharger, and an ECU, wherein the EGR and the supercharger are respectively arranged between the exhaust side and the intake side of the engine body, the engine body is provided with a knock sensor and a crankshaft speed sensor, the intake side of the engine body is connected in sequence with a throttle, an intercooler, and an atmospheric environment sensor upstream, and the exhaust side of the engine body is connected in sequence with a front oxygen sensor, a three-way catalytic converter, and a rear oxygen sensor downstream; the knock sensor is used to detect an engine knock signal, the crankshaft speed sensor is used to detect an engine misfire signal, and the atmospheric environment sensor is used to measure an air humidity value; the ECU is used to control the amount of EGR introduced, the ignition timing of each cylinder of the engine body ignition coil, and the fault instrument display according to the engine knock signal, the humidity signal, and the misfire signal.

[0018] Beneficial effects of the present invention:

[0019] The present invention adds an atmospheric environment sensor to measure humidity to execute relevant compensation correction strategies, and then combines with the ECU to monitor the knock signal intensity and misfire deceleration intensity of each cylinder of the engine in real time, so as to realize the strategy of executing dynamic EGR and single-cylinder ignition advance angle compensation when the engine is actually running, and solves the problem that the in-cylinder combustion cycle compensation control in the prior art is not fully considered when running under special environments, effectively reduces the fluctuation rate of the engine's in-cylinder combustion cycle, and improves the engine operation stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flow chart of a natural gas engine cylinder combustion cycle compensation control method.

[0021] Figure 2 The present invention is a judgment logic block diagram of a natural gas engine cylinder combustion cycle compensation control method.

[0022] Figure 3 The present invention is a schematic diagram of a natural gas engine cylinder combustion cycle compensation control system.

[0023] Figure 4 The present invention is a signal connection diagram of a natural gas engine cylinder combustion cycle compensation control system.

[0024] In the figure, 1-engine body; 2-intake side; 3-exhaust side; 4-EGR; 5-throttle; 6-intercooler; 7-supercharger; 8-three-way catalytic converter; 9-front oxygen sensor; 10-rear oxygen sensor; 11-atmospheric environment sensor; 12-knock sensor; 13-crankshaft speed sensor. DETAILED DESCRIPTION

[0025] In order to explain the technical content, purpose and effect of the present invention in detail, the following is an explanation in combination with embodiments and accompanying drawings. In the description of the embodiments, it should be understood that the terms indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0026] Example 1

[0027] like Figure 1 , Figure 2 As shown, a natural gas engine cylinder combustion cycle compensation control method according to a specific implementation of this scheme includes the following steps:

[0028] S1: Perform bench knock calibration, bench misfire calibration, and vehicle misfire calibration, and record the preset signals of misfire and knock respectively.

[0029] Knock calibration: Complete knock calibration identification on the performance prototype and complete knock consistency verification on 3 to 4 engines to ensure that real engine knock can be identified normally and corresponding protection measures can be taken.

[0030] Misfire calibration: Complete preliminary misfire calibration on the performance prototype and complete misfire consistency verification on 3 to 4 complete vehicles to ensure that when the engine actually misfires, it can be properly identified and appropriate protective measures can be taken.

[0031] S2: Detect the engine knock signal through the knock sensor, detect the engine misfire signal through the crankshaft speed sensor, compare them with the preset signals of misfire and knock, and judge whether it is knock or misfire. If it is knock and / or misfire, correct the EGR rate and ignition advance angle according to the knock signal and misfire signal; if it is neither knock nor misfire, enter S3.

[0032] Specifically, the correction of the EGR rate and the ignition advance angle according to the knock signal and the misfire signal includes the following execution steps:

[0033] S201: If it is judged that there is knock but not misfire, the ignition advance angle of the single cylinder is reduced or EGR is increased until the knock is normal, and then it is judged whether there is misfire. If there is misfire, the process goes to S202;

[0034] S202: If misfire does not cause knock, increase the ignition advance angle or reduce EGR for each cylinder until misfire becomes normal, and then determine whether there is knock. If there is knock, proceed to S201;

[0035] S203: If both detonation and misfire occur, the ignition advance angle of the single cylinder is increased or decreased, and then it is determined whether there is detonation or misfire. If there is detonation or misfire, an abnormal operation signal of the whole vehicle is prompted, and the engine torque is limited to the limit threshold.

[0036] S3: Measure the air humidity value through the atmospheric environment sensor, compare it with the preset air humidity value, and determine whether the current humidity is abnormal. If the humidity is abnormal, correct the EGR rate and ignition advance angle, and then return to S2; if the humidity is normal, the normal operation signal of the whole vehicle is prompted.

[0037] Specifically, the EGR rate and ignition advance angle are corrected, including the following steps: if the humidity is higher than the preset value t1, the single bar increases the ignition advance angle or reduces the EGR; if the humidity is lower than the preset value t2, the single bar reduces the ignition advance angle or increases the EGR.

[0038] The working principle of this embodiment is: when the engine is running, the knock sensor detects the engine knock, the crankshaft speed sensor detects the engine misfire, and the atmospheric environment sensor measures the air humidity. The engine ECU knock monitoring module and misfire monitoring module always monitor the engine running status. Under normal conditions, the engine does not knock or misfire. The knock monitoring module and the misfire monitoring module monitor related parameters below the fault threshold and do not perform any protection operations. The ECU measures the humidity through the atmospheric environment sensor to determine whether to execute the humidity compensation strategy to further improve the combustion in the cylinder and reduce the cycle fluctuation rate. If the humidity compensation is performed, it is necessary to perform a knock misfire judgment and execute the subsequent related processes to avoid over-compensation. When the engine is not working properly, for example, when the vehicle enters a special environment, such as a high temperature and high humidity area, the air humidity content is too high, and the high humidity gas enters the cylinder, resulting in poor combustion. The misfire monitoring module monitors the misfire situation of each cylinder and determines whether to increase the ignition advance angle of a single cylinder or reduce EGR to suppress the misfire. At the same time, the knock monitoring module monitors the knock situation of each cylinder to avoid the knock caused by the execution of the misfire compensation strategy. When the vehicle is added with inferior gas, such as low methane content, high ethane or other low octane gas content, it is very easy to knock when the engine is running. The knock monitoring module monitors the knock of each cylinder. The misfire monitoring module monitors the misfire situation of each cylinder to avoid misfire after the knock compensation strategy is executed; when the whole vehicle triggers the knock protection strategy and the misfire protection strategy at the same time, the knock monitoring module and the misfire monitoring module are used to judge the knock and misfire situation of each cylinder and whether to reduce or increase the ignition advance angle of each cylinder. If neither can be suppressed, it means that the engine has entered an abnormal working state. The user is prompted to repair by limiting torque, turning on the light, etc., to avoid damage or other adverse effects caused by the engine running continuously in an abnormal state.

[0039] In summary, this embodiment implements relevant compensation correction strategies by adding an atmospheric environment sensor to measure humidity, and then combines the ECU to monitor the knock signal intensity and misfire deceleration intensity of each cylinder of the engine in real time, so as to implement the strategy of dynamic EGR and single-cylinder ignition advance angle compensation when the engine is actually running, and solves the problem of incomplete consideration of the in-cylinder combustion cycle compensation control when running in special environments in the prior art, which can more effectively solve the knock and misfire problems, reduce the fluctuation rate of the engine cylinder combustion cycle, and improve the engine operation stability.

[0040] Example 2

[0041] This embodiment is based on the first embodiment and discloses a natural gas engine cylinder combustion cycle compensation control system. Figure 3-4 As shown, Figure 3This is a schematic diagram of the system architecture of the invention, which shows the layout and working status of the natural gas engine. It includes: an engine body 1, an EGR4, a supercharger 7, and an ECU. The EGR4 and supercharger 7 are respectively arranged between the exhaust side 3 and the intake side 2 of the engine body 1. The engine body 1 is provided with a knock sensor 12 and a crankshaft speed sensor 13. The intake side 2 of the engine body 1 is connected to a throttle valve 5, an intercooler 6, and an atmospheric environment sensor 11 in sequence upstream. The exhaust side 3 of the engine body 1 is connected to a front oxygen sensor 9, a three-way catalytic converter 8, and a rear oxygen sensor 10 in sequence downstream.

[0042] The knock sensor 12 is used to detect the engine knock signal, the crankshaft speed sensor 13 is used to detect the engine misfire signal, and the atmospheric environment sensor 11 is used to measure the air humidity value; the ECU is used to control the EGR introduction amount, the ignition timing of each cylinder of the engine body ignition coil, and the fault instrument display according to the engine knock signal, humidity signal, and misfire signal.

[0043] When the engine is operating normally, the high-pressure and high-temperature gas generated by the combustion of the engine body 1 pushes the piston to reciprocate and converts chemical energy into kinetic energy. Part of the exhaust gas is drained back into the cylinder, namely, exhaust gas recirculation EGR, and the other part of the exhaust gas is purified by the three-way catalytic converter TWC8 before being discharged into the atmosphere.

[0044] Although the present invention has been described in detail above with specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A natural gas engine cylinder combustion cycle compensation control method, characterized in that: include: S1: Perform bench knock calibration, bench misfire calibration, and vehicle misfire calibration, and record the preset signals of misfire and knock respectively; S2: Detect the engine knock signal through the knock sensor, detect the engine misfire signal through the crankshaft speed sensor, compare with the preset signals of misfire and knock, and judge whether it is knock or misfire at present. If it is knock and / or misfire, correct the EGR rate and ignition advance angle according to the knock signal and misfire signal; if it is neither knock nor misfire, enter S3; S3: Measure the air humidity value through the atmospheric environment sensor, compare it with the preset air humidity value, and determine whether the current humidity is abnormal. If the humidity is abnormal, correct the EGR rate and ignition advance angle, and then return to S2; if the humidity is normal, the normal operation signal of the whole vehicle is prompted.

2. The natural gas engine cylinder combustion cycle compensation control method according to claim 1, characterized in that: In S2, the EGR rate and ignition advance angle are corrected according to the knock signal and misfire signal, specifically including: S201: If it is judged that there is knock but not misfire, the ignition advance angle of the single cylinder is reduced or EGR is increased until the knock is normal, and then it is judged whether there is misfire. If there is misfire, enter S202; S202: If misfire does not cause knock, increase the ignition advance angle or reduce EGR for each cylinder until misfire becomes normal, and then determine whether there is knock. If there is knock, proceed to S201; S203: If both detonation and misfire occur, the ignition advance angle of the single cylinder is increased or decreased, and then it is determined whether there is detonation or misfire. If there is detonation or misfire, an abnormal operation signal of the whole vehicle is prompted, and the engine torque is limited to the limit threshold.

3. The natural gas engine cylinder combustion cycle compensation control method according to claim 1, characterized in that: In S4, the EGR rate and ignition advance angle are corrected, including: If the humidity is higher than the preset value t1, the horizontal bar increases the ignition advance angle or reduces EGR; If the humidity is lower than the preset value t2, the single bar reduces the ignition advance angle or increases EGR.

4. A natural gas engine cylinder combustion cycle compensation control system, which adopts the method of claim 1, characterized in that: include: An engine body, an EGR, a supercharger, and an ECU, wherein the EGR and the supercharger are respectively arranged between the exhaust side and the intake side of the engine body, the engine body is provided with a knock sensor and a crankshaft speed sensor, the intake side of the engine body is connected in sequence with a throttle, an intercooler, and an atmospheric environment sensor upstream, and the exhaust side of the engine body is connected in sequence with a front oxygen sensor, a three-way catalytic converter, and a rear oxygen sensor downstream; The knock sensor is used to detect engine knock signals, the crankshaft speed sensor is used to detect engine misfire signals, and the atmospheric environment sensor is used to measure air humidity values; The ECU is used to control the amount of EGR introduced, the ignition timing of each cylinder of the engine body ignition coil, and the fault instrument display according to the engine knock signal, humidity signal, and misfire signal.

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